For ease of use, GRBL is tough to beat. It doesn't require a dedicated computer, and it performs well. That said, if you need a fuller set of features, like cutter compensation, then Linux CNC is much more standards-compliant. For most people, particularly beginners, GRBL is the way to go.

The CAM Workbench is used to produce machine instructions for CNC machines from a FreeCAD 3D model. These produce real-world 3D objects on CNC machines such as mills, lathes, lasercutters, or similar. Typically, instructions are a G-code dialect.

You simply need a computer that will run the software needed to operate your CNC. There are three types of software needed to operate a CNC. Design software (CAD) is used to create project designs. CAM (computer-aided machining) software is used to generate tool paths and convert them into gcode.